Grinding roll wheel with tungsten carbide

ABSTRACT

A grinding roll wheel includes an annular body having a front surface, a rear surface, a circumferential surface, and a central cavity. Tungsten carbide is layered or otherwise attached onto a circumferential surface. The tungsten carbide can be applied to the circumferential surface with a MIG weld, a weave weld, or a stringer bead. The grinding roll wheel of the present disclosure may be implemented into a roller mill for comminuting feed material. Grain, ore, gravel, plastic, and the like may be used as the feed material. If grain is used, flour may be produced by comminuting the grain.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to provisional patent application U.S. Ser. No. 62/779,624, filed Dec. 14, 2018. The provisional patent application is herein incorporated by reference in its entirety, including without limitation, the specification, claims, and abstract, as well as any figures, tables, appendices, or drawings thereof

FIELD OF THE INVENTION

The present invention relates generally to an apparatus and corresponding method of use in at least the steel, aluminum, brass, copper, paper and textile industries. More particularly, but not exclusively, the present invention relates to a grinding roll wheel with tungsten carbide for producing coils and plates of a specific thickness and surface finish, starting from a stock material or a slab.

BACKGROUND OF THE INVENTION

The background description provided herein gives context for the present disclosure. Work of the presently named inventors, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art.

Roller mills are mills that use cylindrical rollers or rings, either in opposing pairs or against flat plates, to crush or grind various materials, such as grain, ore, gravel, plastic, and the like. Roller grain mills are an alternative to traditional millstone arrangements in gristmills. Roller mills for rock complement other types of mills, such as ball mills and hammermills, in such industries as the mining and processing of ore and construction aggregate, cement milling, and recycling.

There exists a need in the art for roller mills that have grinding roll wheels that have increased reliability and durability in order to more efficiently comminute feed material.

SUMMARY OF THE INVENTION

Therefore, it is a primary object, feature, or advantage of the present invention to improve on or overcome the deficiencies in the art.

It is still yet a further object, feature, or advantage of the present invention to provide a grinding roll wheel that may be used in a wide variety of applications.

It is still yet a further object, feature, or advantage of the present invention to provide a safe and cost effective grinding roll wheel that requires little maintenance.

It is still yet a further object, feature, or advantage of the present invention to practice methods which facilitate use, manufacture, assembly, and repair of a grinding roll wheel accomplishing some or all of the previously stated objectives.

It is still yet a further object, feature, or advantage of the present invention to provide a grinding roll wheel that is aesthetically pleasing.

It is still yet a further object, feature, or advantage of the present invention to incorporate a grinding roll wheel into a roller mill that accomplishes some or all of the previously stated objectives.

The previous objects, features, and/or advantages of the present invention, as well as the following aspects and/or embodiments, are not exhaustive and do not limit the overall disclosure. No single embodiment need provide each and every object, feature, or advantage. Any of the objects, features, advantages, aspects, and/or embodiments disclosed herein can be integrated with one another, either in full or in part.

According to some aspects of the present disclosure, a grinding roll wheel comprises an annular body having a front surface, a rear surface, a circumferential surface, and a central cavity and tungsten carbide inserts within the circumferential surface. The central cavity can be tapered. The annular body can have an outer diameter of 50 or 54 inches. The tungsten carbide inserts can be symmetrically arranged in rows about an axial axis passing through the central cavity or asymmetrically arranged on the circumferential surface. The tungsten carbide inserts can be applied to the circumferential with a MIG weld, a weave, or a stringer. The grinding roll wheel can be formed of a material selected from the group consisting of mild steel, carbon steel, alloyed steel, stainless steel, and any combination thereof.

According to some additional aspects of the present disclosure, the grinding roll wheel further comprises a chamfered edge between the front surface and the circumferential surface and/or mounting apertures passing through the front surface of the annular body for bolting the grinding roll wheel to a roller mill.

According to some other aspects of the present disclosure, a roller mill can comprise a mill feed inlet for receiving a feed material, a chamber including the grinding roll wheel according to any one or more of the aspects described above, an additional grinding roll wheel, a grinding table, and a mill outlet for transporting comminuted particulate.

According to some additional aspects of the present disclosure, the roller mill further comprises a hydraulic system for lifting the grinding roll wheels from a use position to a non-use position; a heater for drying the feed material within the chamber; a fan for expelling the comminuted particulate within the chamber through the mill outlet; a separator; and/or a scraper blade or an auger for preventing the accumulation of the comminuted particulate on the grinding roll wheel.

According to some other aspects of the present disclosure, a method of crushing or grinding a feed material comprises providing the feed material and the roller mill described above, rotating the grinding roll wheel around an axial axis passing through the central cavity, and allowing the feed material to contact the circumferential surface of the annular body.

According to some additional aspects of the present disclosure, the method further comprises powering the roller mill with a motor and/or drying the feed material. The feed material can be grain and used to produce flour.

These and/or other objects, features, advantages, aspects, and/or embodiments will become apparent to those skilled in the art after reviewing the following brief and detailed descriptions of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a front, upper perspective view of a grinding roll wheel with tungsten carbide inserts, according to some aspects of the present disclosure.

FIG. 2 shows a front plan/elevation view of the grinding roll wheel with tungsten carbide inserts of FIG. 1, according to some aspects of the present disclosure.

FIG. 3 shows a side plan view of the grinding roll wheel with tungsten carbide inserts of FIG. 1, according to some aspects of the present disclosure.

FIG. 4 shows a side elevation view of the grinding roll wheel with tungsten carbide inserts of FIG. 1, according to some aspects of the present disclosure.

FIG. 5 shows a front, upper perspective view of an alternative grinding roll wheel with tungsten carbide ridges, according to some aspects of the present disclosure.

FIG. 6 shows a detailed cross-sectional view of the grinding roll wheel which emphasizes the tungsten carbide and steel layers of the tungsten carbide ridges, according to some aspects of the present disclosure.

FIG. 7 shows a perspective view of a roller mill incorporating the grinding roll wheel of FIG. 1, according to some aspects of the present disclosure.

FIG. 8 shows a perspective view of a weld ring, according to some aspects of the present disclosure.

Several embodiments in which the present invention may be practiced are illustrated and described in detail, wherein like reference characters represent like components throughout the several views. The drawings are presented for exemplary purposes and may not be to scale, unless otherwise indicated, and thus proportions of features in the drawings shall not be construed as evidence of actual proportions.

DETAILED DESCRIPTION OF THE INVENTION Definitions—Introductory Matters

The following definitions and introductory matters are provided to facilitate an understanding of the present invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present invention pertain.

The terms “a,” “an,” and “the” include both singular and plural referents.

The term “or” is synonymous with “and/or” and means any one member or combination of members of a particular list.

The terms “invention” or “present invention” as used herein are not intended to refer to any single embodiment of the particular invention but encompass all possible embodiments as described in the specification and the claims.

The term “about” as used herein refers to slight variations in numerical quantities with respect to any quantifiable variable. One of ordinary skill in the art will recognize inadvertent error can occur, for example, through use of typical measuring techniques or equipment or from differences in the manufacture, source, or purity of components. The claims include equivalents to the quantities whether or not modified by the term “about.”

The term “configured” describes an apparatus, system, or other structure that is constructed to perform or capable of performing a particular task or to adopt a particular configuration. The term “configured” can be used interchangeably with other similar phrases such as constructed, arranged, adapted, manufactured, and the like.

Terms characterizing a sequential order (e.g., first, second, etc.), a position (e.g., top, bottom, lateral, medial, forward, aft, etc.), and/or an orientation (e.g., width, length, depth, thickness, vertical, horizontal, etc.) are referenced according to the views presented. Unless context indicates otherwise, these terms are not limiting. The physical configuration of an object or combination of objects may change without departing from the scope of the present invention.

As would be apparent to one of ordinary skill in the art, mechanical, procedural, or other changes may be made without departing from the spirit and scope of the invention. The scope of the invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

“Carbon steel” is a steel with carbon content up to 2.1% by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states: steel is classified to be carbon steel when: no minimum content is specified or required for chromium, cobalt, molybdenum, nickel, niobium, titanium, tungsten, vanadium, zirconium, or any other element to be added to obtain a desired alloying effect; the specified minimum for copper does not exceed 0.40 percent; or the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65, silicon 0.60, copper 0.60. The term “carbon steel” may also be used in reference to steel which is not stainless steel; in this use carbon steel may include alloy steels.

“Mild steel” (iron containing a small percentage of carbon, strong and tough but not readily tempered), also known as plain-carbon steel and low-carbon steel, contains approximately 0.05-0.30% carbon, making it malleable and ductile. Mild steel has a relatively low tensile strength, but it is cheap and easy to form; surface hardness can be increased through carburizing.

Overview

Referring now to FIGS. 1-6, a grinding roll wheel 10 includes an annular body 12 having a front surface 16, a rear surface (not enumerated, as the rear surface is essentially a mirror image of the front surface 16), a circumferential surface 18, and a central, tapered cavity 14. It may be preferred that the annular body 12 has an outer diameter of 50 or 54 inches. A chamfered edge 20 may be included between the front surface 16 and the circumferential surface 18. Mounting apertures 24 help secure the grinding roll wheel 10 within a rolling mill or other desired location and are typically located in the front surface 16 of the annular body 12. The mounting apertures 24 may be threaded or unthreaded and may receive any type of known fastening device, such as screws, nuts, bolts, rivets, washers, any other known fastening mechanisms, or any combination thereof which may be used to facilitate fastening.

As seen in FIGS. 1-4, tungsten carbide inserts 22 can be positioned within, attach to, form integrally with, placed on, or are otherwise associated with the circumferential surface 18. The tungsten carbide inserts 22 can be symmetrically arranged in rows about an axial axis passing through the central cavity 14 or asymmetrically arranged on the circumferential surface 18.

As seen in FIGS. 5-6, tungsten carbide can be applied to or otherwise comprise ridges 23 which help form the outer portion of the circumferential surface 18. The ridges 23, for example, can be formed tungsten carbide layers 23′ and mild steel layers 23″. As the carbon percentage content rises, steel has the ability to become harder and stronger through heat treating; however, it becomes less ductile. Regardless of the heat treatment, a higher carbon content reduces weldability. In carbon steels, the higher carbon content lowers the melting point. Thus, to better control the melting point and retain a desirable hardness with appropriate abrasive properties, it is preferred (however not required) to alternate the layers which comprise tungsten carbide 23′ and mild steel 23″, as shown.

Tungsten carbide may be attached or directly welded to the grinding roll wheel 10 with, for example, a metal inert gas (MIG) weld, a weave, or a stringer. These ways of embedding tungsten carbide onto the grinding roll wheel 10 can be used to improve the effectiveness of depositing extremely hard tungsten carbide particles onto circumferential surface 18 of the annular body 12.

To form a strong joint between the tungsten carbide inserts 22 and the grinding wheel 10 that will hold under stress from any angle, careful attention should be given when forming a bead from drawing a weld pool (e.g., the result of a welding arc struck between an electrode and the material being welded) after the electrode. For example, an appropriate length of welding arc, rate of electrode movement, width of the bead, and an angle (position) at which the electrode is held should be determined. When various electrode diameters are needed, the length of the welding arc should change accordingly. The normal arc length of covered electrodes may, for example, vary between 3/16″ to ¼″. Choosing an arc length below or above these nominal values may result in the arc shorting out or excessive spattering, respectively. Spattering is small solidified metal particles that are formed from the filler metal used for the weld. Even with maintaining proper arc length, a constant, forward speed is necessary to form a good bead and ensure a uniform height, width, and ripple spacing of the bead.

There are two forms of beads that can be placed on the material, a stringer bead or a weaving bead (to form a weave weld). To form a stringer bead, the bead should be drawn in a forward direction. The speed of drawing the bead should be fast enough so that the weld does not bum through the material but slow enough to allow the weld pool to accumulate to approximately two to three times the diameter of the electrode. For example, if the electrode diameter is ¼″, a properly formed stringer bead will be ½″ to ¾″ in width.

To form a weaving bead, the electrode must be moved back and forth while drawing the bead forward. Using this method, the bead may be formed with any desired width. To maintain adequate bead control, the width of the bead should be kept to no more than six times the electrode diameter. For example, if the electrode diameter is ¼″, the bead should be kept to a maximum of 1 and ½″ in width.

The angle at which the electrode is held should be kept tipped in the direction of travel, such as at a 20-degree angle, to allow the arc to force the molten metal to the back of the weld pool and thereby allow the desired bead ripples to form. When forming a bead, the electrode should be parallel to the weld line. It may be necessary to first clean the end of the electrode and position the electrode in a holder. An initial arc should then be struck approximately ⅜″ ahead of the location where the bead should be formed. The electrode should be moved rapidly to the location where the weld pool should begin to form. This will allow the arc to stabilize prior to the initial formation of the weld pool. With a steady arc, begin moving the electrode in a straight line in the direction of the weld line.

Forward motion begins when the bead width reaches the desired size. With the desired size reached, the electrode should be pulled slightly forward and allow the pool to grow in size again. After the proper rate of advancing the electrode has been reached, the electrode should be moved forward in one continuous motion. The speed of the electrode is primarily determined by the desired bead width and formation of bullet-nose-shaped ripples in the back of the molten weld pool. After the weld is complete, the quantity of the weld metal buildup and the shape of the weld bead ripples will help inform a welder whether the speed of the electrode should be altered. Correct height of the weld is shown by the formation of the bullet-nose shaped ripples. The formation of these ripples can only be achieved by maintaining the proper forward speed. These ripples are the result of metal buildup above the surface of the metal. If the bead takes on a pointed shape, then the speed of travel is too fast. If the bead is straight or does not have curvature, the speed of travel is too slow.

A properly drawn stringer bead should be even in width, height, and ripples that are bullet-nose shaped. For example, the bead height may, preferably, be approximately one quarter of the bead width. Even while maintaining the proper speed, angle, and position of the electrode, an unsatisfactory bead can still be formed if the proper current setting is not maintained. If the current has been set too low, the bead may not penetrate the metal and may pool too high. With the current too high, the electrode may be excessively hot and may produce enormous amounts of splatter. The bead may also have too much penetration and may even burn through the metal. The resulting weld may be extremely porous with excessive gas pockets and impurities in the bead.

MIG welding is an arc welding process in which a continuous solid wire electrode is fed through a welding gun and into the weld pool, joining the two base materials together. A shielding gas is also sent through the welding gun and protects the weld pool from contamination. MIG welding is a subtype of gas metal arc welding (GMAW).

MIG tungsten carbide embedding is a welding process that deposits extremely hard tungsten carbide particles (70 Rc) in the weld puddle of a hardfacing wire as it is applied. MIG tungsten carbide incorporates intact tungsten carbide particles for maximum abrasion resistance, is more abrasion resistant than chromium carbide, is easy and economical to apply, provides wear life compared to typical hardfacing wires, and may be used in extreme abrasion environments.

For example, for severe abrasion applications, the specific wires may be used to assist MIG carbide embedding, such as a wire that consists of a vibratory feeder and a standard semi-automatic MIG gun, that delivers metered tungsten carbide particles to a molten weld pool at precisely the right moment prior to the puddle freezing. The result is a weld deposit filled with tungsten carbide.

While chromium carbide has served industry adequately for many years, more recent production demands on parts and equipment have dictated a harder, more wear resistant solution. MIG carbide embedding can offer two to eight times better wear life than typical hardfacing alloys and can be deposited at one-third the cost of tungsten carbide hardfacing wires.

Unlike stick and flux-cored electrodes, which have higher amounts of special additives, the solid MIG wire does not combat rust, dirt, oil or other contaminants very well. Thus, it may be necessary to use a metal brush or grinder, clean down to bare metal before striking an arc, and connect any work clamps to clean metal to reduce the risk of any electrical impedance affecting wire feeding performance before starting the welding process. To ensure strong welds on thicker metal, it may be desirable to bevel the grinding wheel to ensure the weld fully penetrates to the base metal.

To perform gas metal arc welding, the basic necessary equipment is a welding gun, a wire feed unit, a welding power supply, a welding electrode wire, and a shielding gas supply.

The typical gas metal arc welding gun has a number of key parts—a control switch, a contact tip, a power cable, a gas nozzle, an electrode conduit and liner, and a gas hose. The control switch, or trigger, when pressed by the welder, initiates the wire feed, electric power, and the shielding gas flow, causing an electric arc to be struck. The contact tip, normally made of copper and sometimes chemically treated to reduce spatter, is connected to the welding power source through the power cable and transmits the electrical energy to the electrode while directing it to the weld area. It must be firmly secured and properly sized, since it must allow the electrode to pass while maintaining electrical contact. On the way to the contact tip, the wire is protected and guided by the electrode conduit and liner, which help prevent buckling and maintain an uninterrupted wire feed. The gas nozzle directs the shielding gas evenly into the welding zone. Inconsistent flow may not adequately protect the weld area. Larger nozzles provide greater shielding gas flow, which is useful for high current welding operations that develop a larger molten weld pool. A gas hose from the tanks of shielding gas supplies the gas to the nozzle. Sometimes, a water hose is also built into the welding gun, cooling the gun in high heat operations.

The wire feed unit supplies the electrode to the work, driving it through the conduit and on to the contact tip. Most models provide the wire at a constant feed rate, but more advanced machines can vary the feed rate in response to the arc length and voltage. Some wire feeders can reach feed rates as high as 1200 inches per minute, but feed rates for semiautomatic gas metal arc welding typically range from 75-400 inches per minute.

Most applications of gas metal arc welding use a constant voltage power supply. As a result, any change in arc length (which is directly related to voltage) results in a large change in heat input and current. A shorter arc length causes a much greater heat input, which makes the wire electrode melt more quickly and thereby restore the original arc length. This helps operators keep the arc length consistent even when manually welding with hand-held welding guns. To achieve a similar effect, sometimes a constant current power source is used in combination with an arc voltage-controlled wire feed unit. In this case, a change in arc length makes the wire feed rate adjust to maintain a relatively constant arc length. In rare circumstances, a constant current power source and a constant wire feed rate unit might be coupled, especially for the welding of metals with high thermal conductivities, such as aluminum. This grants the operator additional control over the heat input into the weld, but requires significant skill to perform successfully. The present disclosure contemplates additional power supplies with varying known functions or advantages may be used in conjunction with or in lieu of the power supply described above to meet the needs of the specific weld to be performed.

Alternating current is rarely used with gas metal arc welding; instead, direct current is employed and the electrode is generally positively charged. Since the anode tends to have a greater heat concentration, this results in faster melting of the feed wire, which increases weld penetration and welding speed. The polarity can be reversed only when special emissive-coated electrode wires are used, but since these are not popular, a negatively charged electrode is rarely employed.

Electrode selection is based primarily on the composition of the metal being welded, the process variation being used, annular body design and the material surface conditions. Electrode selection greatly influences the mechanical properties of the weld and is a key factor of weld quality. In general, the finished weld metal should have mechanical properties similar to those of the base material with no defects such as discontinuities, entrained contaminants or porosity within the weld. To achieve these goals a wide variety of electrodes exist. All commercially available electrodes contain deoxidizing metals such as silicon, manganese, titanium and aluminum in small percentages to help prevent oxygen porosity. Some contain denitriding metals such as titanium and zirconium to avoid nitrogen porosity. Depending on the process variation and base material being welded the diameters of the electrodes used in gas metal arc welding typically range from 0.7 to 2.4 millimeters (0.028-0.095 inches) but can be as large as 4 millimeters (0.16 inches). The smallest electrodes, generally up to 1.14 millimeters (0.045 inches) are associated with the short-circuiting metal transfer process, while the most common spray-transfer process mode electrodes are usually at least 0.9 millimeters (0.035 inches).

Shielding gases are necessary for gas metal arc welding to protect the welding area from atmospheric gases such as nitrogen and oxygen, which can cause fusion defects, porosity, and weld metal embrittlement if they come in contact with the electrode, the arc, or the welding metal. This problem is common to all arc welding processes; for example, in the older shielded-metal arc welding process, the electrode is coated with a solid flux which evolves a protective cloud of carbon dioxide when melted by the arc. In gas metal arc welding, however, the electrode wire does not have a flux coating, and a separate shielding gas is employed to protect the weld. This eliminates slag, the hard residue from the flux that builds up after welding and must be chipped off to reveal the completed weld.

Before striking an arc, cables should be checked to make sure all of the cable connections are tight fitting and free of fraying or other damage. Additionally, the electrode polarity should eb selected. MIG welding, for example, requires DC electrode positive, or reverse polarity. The polarity connections are usually found on the inside of the machine.

Additionally, the gas flow should be set after turning on the shielding gas. The desirable rate of shielding-gas flow depends primarily on weld geometry, speed, current, the type of gas, and the metal transfer mode. Welding flat surfaces requires higher flow than welding grooved materials, since gas disperses more quickly. Faster welding speeds, in general, mean that more gas must be supplied to provide adequate coverage. Additionally, higher current requires greater flow, and generally, more helium is required to provide adequate coverage than if argon is used. Perhaps most importantly, the four primary variations of gas metal arc welding have differing shielding gas flow requirements—for the small weld pools of the short circuiting and pulsed spray modes, about 20 to 25 cubic feet per hour is generally suitable, whereas for globular transfer, around 30 feet per cubic hour is preferred. The spray transfer variation normally requires more shielding-gas flow because of its higher heat input and thus larger weld pool. Typical gas-flow amounts are approximately 40 to 50 cubic feet per hour. If leaks in the gas hose are suspected, a soapy water solution could be applied. Bubbles may help indicate if a leak is present, in which case the hose should be discarded and a new hose should be installed.

Additionally, tension in the drive rolls and the wire spool hub should be checked. Too much or too little tension on either the drive rolls or the wire spool hub can lead to poor wire feeding performance. In this case, the tension should be adusted.

Additionally, consumables should be checked in case they have been consumed by previous welds. It may then be desired to remove excess spatter from contact tubes, replace worn contact tips and liners, and discard the wire if it appears rusty.

For steel, there are two common wire types. It may be preferred to use an AWS classification ER70S-3 for all-purpose welding. It may be preferred to use an ER70S-6 wire when more deoxidizers are needed for welding on dirty or rusty steel. As for the wire diameter, it may be preferred to use a 0.030-inch diameter makes a good all-around choice for welding the tungsten carbide onto the grinding wheel. For welding thinner tungsten carbide inserts, a 0.023-inch wire may be used to reduce heat input. For welding thicker tungsten carbide inserts at higher total heat levels, a 0.035-inch wire may be used.

Stick-out is the length of unmelted electrode extending from the tip of the contact tube, and it does not include arc length. The ideal stick-out will create a “sizzling” sound during operation. This may occur at ⅜″, but if the arc sounds irregular, the length of the stick-out could be adjusted.

It may also be necessary to select the voltage level and wire feed speed to be used during the welding process. How much voltage and amperage a weld requires depends on numerous variables, including metal thicknesses, type of metal, grinding wheel configuration, welding position, shielding gas and wire diameter speed (among others). Some wire feed systems have a convenient reference chart located on the inside of the door housing. Other wire feed systems are automated and depend on the wire diameter being used and the thickness of tungsten carbide inserts to be welded. The welding arc may be fine-tuned to suit personal preference.

The choice of a shielding gas depends on several factors, most importantly: the type of material being welded, and the process variation being used. Pure inert gases such as argon and helium are only used for nonferrous welding; with steel they do not provide adequate weld penetration (argon) or cause an erratic arc and encourage spatter (with helium). Pure carbon dioxide, on the other hand, allows for deep penetration welds but encourages oxide formation, which adversely affect the mechanical properties of the weld. Its low cost makes it an attractive choice, but because of the reactivity of the arc plasma, spatter is unavoidable and welding thin materials is difficult. As a result, argon and carbon dioxide are frequently mixed in a 75 percent argon/25 percent CO₂ blend (also called “75/25” or “C25”) to 90 percent argon/25 percent CO₂ blend. C25 may work as the best “all purpose” shielding gas for carbon steel. Generally, in short circuit gas metal arc welding, higher carbon dioxide content increases the weld heat and energy when all other weld parameters (volts, current, electrode type and diameter) are held the same. As the carbon dioxide content increases over 20%, spray transfer gas metal arc welding becomes increasingly problematic, especially with smaller electrode diameters.

Argon is also commonly mixed with other gases, oxygen, helium, hydrogen and nitrogen. The addition of up to 5% oxygen (like the higher concentrations of carbon dioxide mentioned above) can be helpful in welding stainless steel, however, in most applications carbon dioxide is preferred. Increased oxygen makes the shielding gas oxidize the electrode, which can lead to porosity in the deposit if the electrode does not contain sufficient deoxidizers. Excessive oxygen, especially when used in application for which it is not prescribed, can lead to brittleness in the heat affected zone. Argon-helium mixtures are extremely inert, and can be used on nonferrous materials. A helium concentration of 50-75% raises the required voltage and increases the heat in the arc, due to helium's higher ionization temperature. Hydrogen is sometimes added to argon in small concentrations (up to about 5%) for welding nickel and thick stainless-steel workpieces. In higher concentrations (up to 25% hydrogen), it may be used for welding conductive materials such as copper. However, it should not be used on steel, aluminum or magnesium because it can cause porosity and hydrogen embrittlement.

Shielding gas mixtures of three or more gases are also available. Mixtures of argon, carbon dioxide and oxygen are marketed for welding steels. Other mixtures add a small amount of helium to argon-oxygen combinations, these mixtures are claimed to allow higher arc voltages and welding speed. Helium also sometimes serves as the base gas, with small amounts of argon and carbon dioxide added. However, because it is less dense than air, helium is less effective at shielding the weld than argon—which is denser than air. It also can lead to arc stability and penetration issues, and increased spatter, due to its much more energetic arc plasma. Helium is also substantially more expensive than other shielding gases. Other specialized and often proprietary gas mixtures claim even greater benefits for specific applications.

A human welder may utilize the push or forehand technique which involves pushing the gun away from (ahead of) the weld puddle. Pushing usually produces lower penetration and a wider, flatter bead because the arc force is directed away from the weld puddle. Pushing usually offers a better view and enables you to better direct wire into the circumferential surface 18. A human welder may also utilize the drag or backhand technique (also called the, pull or trailing technique) where the welding gun is pointed back at the weld puddle and dragged away from the deposited metal. Dragging typically produces deeper penetration and a narrower bead with more buildup.

For MIG welding, travel angle is defined as the angle relative to the gun in a perpendicular position. Normal welding conditions in all positions call for a travel angle of 5 to 15 degrees. Travel angles beyond 20 to 25 degrees can lead to more spatter, less penetration and general arc instability. Work angle is the gun position relative to the angle of the circumferential surface 18, and it varies with each welding position and grinding wheel configuration. For example, a welder may weld from a flat position, a horizontal position, a vertical position, an overhead position, etc. With respect to welding carbide onto the circumferential surface 18, a welder may find it is easiest to weld from a flat or horizontal position. When welding from a horizontal position, the welder may have to adjust the gun angle by up to 15 degrees to account for the effects of gravity.

Using any of the aforementioned methods for embedding tungsten carbide are especially advantageous for creating improved grinding roll wheels 10 because of the high abrasion environments the grinding wheel is subjected to. Typically, rolling mills of this type are almost continuously operated throughout the week. This punishing environment requires strong and resilient material that will not prematurely or unexpectedly deteriorate.

It should be noted that human welders should observe proper safety precautions before using any tungsten carbide embedding process disclosed herein. Welders should make sure they have the proper safety apparel and that any potential fire hazards are removed from the welding area. Basic welding safety apparel includes but is not limited to leather shoes or boots, cuff-less full-length pants, a flame-resistant, long sleeve jacket, leather gloves, a welding helmet, safety glasses and a bandana or “skull cap” to protect the top of the welder's head from sparks and spatter.

The present disclosure contemplates that the welding process may also be substantially automated such that a human welder is not necessary for more than providing inputs to an automated system or for supervisory purposes. Using automated systems to handle the workpieces and the welding gun can speed up the manufacturing process such that carbide can be quickly embedded in a plurality of grinding wheels on an assembly line.

The exemplary roller mill 26 shown in FIG. 7 may be preferred for grinding grain during the manufacture of flour. However, the roller mill 26 is also suitable for grinding any moderately tough material, including minerals, that must be reduced to a very fine powder. Since the roller mill shears the feed material instead of crushing the feed material via direct pressure, the roller mill may be used where material is to be reduced to a moderately fine size but with the minimum of fines.

The roller mill 26 includes a mill feed inlet for introducing raw feed material 28 into the grinding chamber 30 in the base of the roller mill 26 at a rate determined by pressure variations. The chamber 30 includes at least one grinding roll wheel 10 in addition to other grinding roll wheels 10 or traditional grinding roll wheels, a grinding table or floor 32; and plows located ahead of each grinding wheel 10 which direct the material upward and between the grinding rolls and the heavy alloy steel bull ring where it is ground to size. The grinding roll wheels 10 are free to swing out centrifugally which forces them to bear upon and grind the raw material. Being free to pivot, the grinding roll wheels 10 automatically assume the proper position for grinding and need no adjustment to compensate for wear.

Once ground to size, the fine product 34 left from the feed material 28 is swept out of the mill by the controlled air flow from the centrifugal main mill fan. Air suspended, the ground material passes through an adjustable separator (the motor for the separator designated in FIG. 7 as 36). In the separator, an accurate size classification is made which allows product size material to be conveyed away from the grinding mill while larger material is returned for additional grinding. Acceptably sized material, or comminuted particulate, is eventually removed from the airstream through the mill outlet. Typically, a conveyor or product storage bin will be located to accept the comminuted material as the comminuted material exits the chamber 30.

A high efficiency fabric dust collector may be used to aid removing airborne fines which remain entrained in the exhaust gas. The efficiency of the basic roller mill becomes much more efficient after moisture is removed from the feed material by using hot air 38 from a heater, as shown in FIG. 7.

A hydraulic system 40 for lifting the grinding roll wheels 10 from a use position to a non-use position is also shown. The hydraulic system 40 aids in the cleaning and repair of grinding wheels 10 used in the rolling mill 26. The frequency in which the grinding wheels 10 require cleaning or repair may be reduced through the use of a scraper blade or an auger which prevents the accumulation of the comminuted particulate on the grinding roll wheel 26.

Other refinements contemplated by the present disclosure include a recycle line from the dust collector to the heater which enables a further reduction in oxygen level and allows the roller mill 26 to process hazardous dusts in a controlled low oxygen atmosphere and a discharge spout located beneath the roller mill 26 which continuously removes impurities and allows for product beneficiation.

It is to be appreciated the grinding roll wheel 10 can be used in many different types of mills and in many different applications. For example, and without limitation, the grinding roll wheel 10 can be used in a ring-roller type roller mill which includes a weld ring 42 (shown in FIG. 8). The grinding roll wheel 10 can aid the weld ring, which can be stationed on a wall of the roller mill 26 to help pulverize feed material. In another example, and without limitation, the grinding roll wheel 10 can be used with a bowl mill instead of a roller mill, such as that which is disclosed in U.S. Pat. No. 2,079,155, which is herein incorporated by reference in its entirety.

Additionally, and unless otherwise specified in the claims, the present disclosure is not to be limited to the use of tungsten carbide. Other suitable carbides may be used.

From the foregoing, it can be seen that the present invention accomplishes at least all of the stated objectives.

LIST OF REFERENCE NUMERALS

The following reference characters and descriptors are not exhaustive, nor limiting, and include reasonable equivalents. If possible, elements identified by a reference character may replace or supplement any element identified by another reference character.

-   10 grinding roll wheel -   12 annular body -   14 central, tapered cavity -   16 front surface -   18 circumferential surface -   20 chamfered edge -   22 tungsten carbide inserts -   23 ridges -   23′ tungsten carbide layers -   23″ steel layers (e.g. mild steel layers) -   24 mounting apertures for bolts -   26 roller mill -   28 feed material for mill feed inlet -   30 grinding chamber -   32 grinding table or floor -   34 fine product propelled by fan -   36 motor of separator -   38 hot air from heater -   40 hydraulic system -   42 weld ring

The present disclosure is not to be limited to the particular embodiments described herein. The following claims set forth a number of the embodiments of the present disclosure with greater particularity. 

What is claimed is:
 1. A grinding roll wheel, comprising: an annular body having a front surface, a rear surface, a circumferential surface, and a central cavity; and wherein the circumferential surface comprises steel and tungsten carbide.
 2. The grinding roll wheel of claim 1 wherein the central cavity is tapered.
 3. The grinding roll wheel of claim 1 wherein the steel and the tungsten carbide are layered onto the circumferential surface.
 4. The grinding roll wheel of claim 1 wherein the tungsten carbide is formed from tungsten carbide inserts are asymmetrically arranged on the circumferential surface.
 5. The grinding roll wheel of claim 1 wherein the tungsten carbide inserts are welded to the circumferential surface with a metal inert gas (MIG) weld, a weave, or a stringer.
 6. The grinding roll wheel of claim 1 further comprising a chamfered edge between the front surface and the circumferential surface.
 7. The grinding roll wheel of claim 1 further comprising mounting apertures passing through the front surface of the annular body for bolting the grinding roll wheel to a roller mill.
 8. The grinding roll wheel of claim 1 wherein the annular body has an outer diameter of 50 or 54 inches.
 9. The grinding roll wheel of claim 1 wherein the steel is selected from the group consisting of mild steel, alloyed steel, stainless steel, and any combination thereof.
 10. A roller mill comprising: a mill feed inlet for receiving a feed material; a chamber comprising: the grinding roll wheel of claim 1; an additional grinding roll wheel; a grinding table; and a mill outlet for transporting comminuted particulate.
 11. The roller mill of claim 10 further comprising a hydraulic system for lifting the grinding roll wheels from a use position to a non-use position.
 12. The roller mill of claim 10 further comprising a heater for drying the feed material within the chamber.
 13. The roller mill of claim 10 further comprising a fan for expelling the comminuted particulate within the chamber through the mill outlet.
 14. The roller mill of claim 10 further comprising a separator.
 15. The roller mill of claim 10 further comprising a scraper blade or an auger for preventing the accumulation of the comminuted particulate on the grinding roll wheel.
 16. A method of crushing or grinding a feed material comprising: providing the feed material and the roller mill of claim 10; rotating the grinding roll wheel around an axial axis passing through the central cavity; and allowing the feed material to contact the circumferential surface of the annular body.
 17. The method of claim 16 further comprising powering the roller mill with a motor.
 18. The method of claim 16 further comprising drying the feed material.
 19. The method of claim 16 wherein the feed material is grain.
 20. The method of claim 19 further comprising producing flour. 